Samsung Electronics Co. Ltd., as expected, is still the leading manufacturer of smartphones in the United States. Google, Inc.’s (NASDAQ:GOOG) Android platform still rules the roost by a longshot, thanks to the various smartphones that run on the operating system, or OS.

But don’t look now – Apple, Inc. (NASDAQ: AAPL) appears to be sneaking up fast with both the iPhone and iOS.

comScore released a survey of mobile OEMs (original equipment manufacturers) and smartphone platforms, and among all the companies in the respective Top 5, Apple seems to be making the largest quarter-on-quarter improvement.

Compared to the Q1 2012, Apple moved up by 1.4 percent in the June ending Q2 to 15.4 percent. Samsung remained in the lead with 25.6 percent (down 0.4 percent quarter-on-quarter), followed by LG at 18.8 percent. It is possible that Apple could move up significantly in the next two quarters, following widespread rumors of a new iPhone release next month.

The other OEMs in the top five list were Motorola (11.7 percent) and HTC (6.4 percent).

For mobile platforms, Google Android moved up a bit from 51.0 to 51.6 percent quarter-on-quarter, remaining the dominant OS in the American market. Apple remained second, but made a larger increase, up 1.7 percent to 32.4 percent. Also-rans in this category were Research in Motion Ltd.’s (NASDAQ:RIMM) BlackBerry, Microsoft (NASDAQ:MSFT) Windows Phone and Nokia Corp.’s (NASDAQ:NOK) now-outdated Symbian operating system.

It will be infinitely fascinating to see where everything stands after Q3 2012. The statistics above did not include sales of the Samsung Galaxy S3, which launched in the United States just last month. Also, there is a chance the Q3 2012 numbers will include the iPhone 5, provided the September launch rumors are accurate.